FLIR E40 User Manual

Theory of thermography
32
• A selective radiator, for which ε varies with wavelength
According to Kirchhoff’s law, for any material the spectral emissivity and spectral absorp-
tance of a body are equal at any specified temperature and wavelength. That is:
From this we obtain, for an opaque material (since α
λ
+ ρ
λ
= 1):
For highly polished materials ε
λ
approaches zero, so that for a perfectly reflecting materi-
al (i.e. a perfect mirror) we have:
For a graybody radiator, the Stefan-Boltzmann formula becomes:
This states that the total emissive power of a graybody is the same as a blackbody at the
same temperature reduced in proportion to the value of ε from the graybody.
Figure 32.8 Spectral radiant emittance of three types of radiators. 1: Spectral radiant emittance; 2: Wave-
length; 3: Blackbody; 4: Selective radiator; 5: Graybody.
Figure 32.9 Spectral emissivity of three types of radiators. 1: Spectral emissivity; 2: Wavelength; 3: Black-
body; 4: Graybody; 5: Selective radiator.
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FLIR E40 Specifications

General

Resolution	160 x 120 pixels
Accuracy	±2°C or ±2% of reading
Focus	Manual
Image Storage	SD card
Image Frequency	60 Hz
Digital Camera	3.1 MP
Battery operating time	Approx. 4 hours
Operating Temperature	-15°C to +50°C
Storage Temperature	-40°C to +70°C
Spectral Range	7.5 - 13 µm
Field of View	25° x 19°
Display	3.5 in color LCD
Image Modes	Thermal, Visual, MSX
Measurement Presets	Center Spot, Hot Spot, Cold Spot
File format	JPEG
Battery type	Li-Ion battery
Connectivity	USB, Wi-Fi
Thermal Sensitivity	< 0.07°C @ +30°C (+86°F) / 70 mK